Double-sided tape for touch screen panel and manufacturing method thereof

ABSTRACT

The present invention provides a double-sided tape for a touch screen panel which comprises a shock resistant filler layer to exhibit excellent viscosity while being thin and have excellent shock resistance and an excellent waterproof property, and a manufacturing method.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a double-sided tape for a touch screenpanel and a manufacturing method, and more particularly to adouble-sided tape for a touch screen panel which is located between apanel module and a liquid crystal module of a touch screen, exhibitsexcellent viscosity while being thin and has excellent shock resistanceand an excellent waterproof property, and a manufacturing method.

Description of the Related Art

In portable electronic devices such as an electronic note, a cellularphone, PHS, a camera, a music player and the like, double-sided tapesare being used to fix various members and modules, including anattachment of a protection panel of an information display part and acase. The double-sided tapes have required a lot of useful functions inorder to gain competitive advantage in the market, and one of thefunctions requires giving a waterproof property.

Japanese Laid-Open Patent Publication No. 2005-187531 provides adouble-sided tape used to fix parts of an electronic device. Forexample, there is disclosed a double-sided adhesive sheet which has amaximum value of a loss tangent (tanδ) at a temperature region of −40to−15° C., and has an adhesive layer having side adhesive strength to aspecific adhered object of 19N/cm² or more arranged on double sides of asupporter. The double-sided adhesive sheet comprises a specific adhesivelayer to provide excellent adhesion and to exhibit excellent shockresistance which makes it difficult to detach parts due to shock infalling of objects.

However, in attaching rigid bodies as in the attachment of theprotection panel and the case, since double-sided adhesive sheet findsdifficulty in obtaining complete adhesion between the adhered object andan attachment surface, the parts flooded when there were a few gaps.

Japanese Laid-Open Patent Publication No. 2005-281360 provides adouble-sided adhesive tape with excellent adhesion. There is disclosed adouble-sided adhesive tape which refers to a foaming body as a base, andhas an acrylic-based adhesive layer having a maintenance time of 24hours or more in a maintenance test at a temperature of −25° C. or lessand 0° C., wherein the temperature indicates a maximum value of a losstangent (tanδ). The double-sided adhesive tape has excellent adhesion toan adhered object, from which members can be very properly connected inthe attachment between the members.

However, although the foaming body is used as the base, it is difficultto restrain even a few gaps from occurring on an interface between themember and the adhesive layer. Hence, when a gap or a crack throughwhich water can permeate is present on part of the interface, apermeation path is enlarged therefrom. As a result, it is difficult toimplement an excellent waterproof property.

Specifically, portable electronic devices are required to become narrowand thinner according to recent large screens thereof, and as a result,when a narrow tape or a thin tape is required, it is difficult to give asufficient waterproof property to the tape.

SUMMARY OF THE INVENTION Technical Problem

The present invention was made to solve the aforementioned problemoccurring in the prior art, and it is an object of the present inventionto provide a double-sided tape for a touch screen panel which is locatedbetween a panel module and a liquid crystal module of a touch screen,exhibits excellent viscosity while being thin and has excellent shockresistance and an excellent waterproof property, and a manufacturingmethod.

Technical Solution

The present invention provides a double-sided tape for an a touch screenpanel comprising a base film; a shock resistant filler layer formed onthe base film and comprising an acrylic binder and an shock resistantfiller containing 5-60 parts by weight with respect to 100 parts byweight of the acrylic binder; first and second adhesive layers formed anupper side of the shock resistant filler layer and a lower side of thebase film, respectively; and a release layer formed on a lower side ofthe second adhesive layer, wherein the shock resistant filler of theshock resistant filler layer comprises a plurality of hollow fineparticles.

In accordance with another preferable embodiment, the hollow fineparticles may comprise 50-80 parts by weight of calcium carbonate, withrespect to a total of 100 parts by weight, and may further comprise asecond coating film disposed arranged along the circumference of thefirst coating film.

In accordance with another preferable embodiment, the shock resistantfiller layer may comprise 5-60 parts by weight of the shock resistantfiller, with respect to 100 parts by weight of the acrylic binder.

In accordance with another preferable embodiment, a monomer of the firstcoating film may be a copolymer comprising at least one of 15-40 partsby weight of acrylonitrile, with respect to 100 parts by weight of thehollow fine particles, phosphate methacrylate and alkali strippablepolyester acrylate.

In accordance with another preferable embodiment, at least one of thebase film and the shock resistant filler layer may turn black, and theblack coloring agent comprise at least one of carbon black and ironsulfide.

In accordance with another preferable embodiment, the hollow fineparticles comprise: liquid hydrocarbon comprising 1-10 parts by weightof 2-methyl butane and 1-10 parts by weight of 2-methyl propane, withrespect to a total of 100 parts by weight; a first coating film formedof a thermoplastic material comprising a copolymer containing at leastone of 15-40 parts by weight of acrylonitrile, phosphate methacrylate,alkali strippable polyester acrylate, and formed to surround the liquidhydrocarbon; and a second coating film formed of 50-80 parts by weightof calcium carbonate, and formed to surround the first coating film.

An embodiment of the present invention provides a method formanufacturing a double-sided tape for a touch screen panel, comprisingthe steps of: coloring a base film black; forming a shock resistantfiller layer by coating a paste containing a shock resistant fillerhaving an acrylic binder and a plurality of hollow fine particles on anupper side of the base film; forming first and second adhesive layers onan upper side of the shock resistant filler layer and a lower side ofthe base film, respectively; and forming a release layer on a lower sideof the second adhesive layer, wherein the hollow fine particles aremanufactured by the steps of: preparing a hydrogen dispersion byinputting 2-6 parts by weight of liquid hydrocarbon with respect to atotal of 100 parts by weight and a dispersing agent into water;preparing a particulate crystal by inputting 15-40 parts by weight of amonomer into the hydrogen dispersion, with respect to a total of 100parts by weight of the hollow fine particles, and forming a firstcoating film on the circumference of the hydrocarbon; forming anunexpanded microsphere by heating the particulate crystal and removingthe hydrocarbon; and preparing an expanded microsphere by heating theunexpanded microsphere to expand the first coating film.

In accordance with another preferable embodiment, the hollow fineparticles may be manufactured by further comprising the step ofarranging a second coating film containing 50-80 parts by weight ofcalcium carbonate, with respect to a total of 100 parts by weight of thehollow fine particles, on the circumference of the first coating film ofthe expanded microsphere.

In accordance with another preferable embodiment, in the step ofpreparing the hydrogen dispersion, the liquid hydrocarbon may comprise1-10 parts by weight of 2-methylbutane and 1-10 parts by weight of2-methylpropane, with respect to a total of 100 parts by weight of thehollow fine particles.

In accordance with another preferable embodiment, in the step ofpreparing the hydrogen dispersion, the dispersing agent may be asurfactant.

In accordance with another preferable embodiment, in the step ofpreparing the particulate crystal, the monomer may be a copolymer of15-40 parts by weight of acrylonitrile with respect to a total of 100parts by weight of the hollow fine particles, and other acrylic groups.

In accordance with another preferable embodiment, in the step ofpreparing the expanded microsphere, the unexpanded microsphere may beheated at a temperature of 170-190° C.

In accordance with another preferable embodiment, the step of formingthe second coating film may comprise the steps of: inputting theexpanded microsphere and the calcium carbonate into a reactor, andinserting air thereto at a temperature of 130-150° C., thereby floatingthe expanded microsphere and the calcium carbonate inside the reactor;and forming a second coating film while embedding the calcium carbonatein an outer wall of the first coating film of the expanded microsphere.

In accordance with another preferable embodiment, in the step ofcoloring the base film black, at least one of carbon black and ironsulfide may be used as the black coloring agent.

In accordance with another preferable embodiment, in the step of formingthe shock resistant filler layer, the shock resistant filler maycomprise 5-60 parts by weight with respect to 100parts by weight of theacrylic binder.

Effects of the Invention

The double-sided tape for a touch screen panel according to theexemplary embodiment of the present invention exhibits excellentadhesion to an adhered object while being thin and has excellent shockresistance and an excellent waterproof property to effectively preventpenetration of water from a tight gap. Thus, when the double-sided tapeis used in a touch screen panel of a portable electronic device whichhas difficulty in preparing a separate water sealing means because theportable electronic device becomes thin to have strict bulk restrictionin a case thereof, it is able to effectively give a waterproofingfunction to the portable electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a double-sided tape for a touchscreen panel according to an exemplary embodiment of the presentinvention.

FIG. 2 is a graph showing the result of comparing adhesion tests betweenembodiments of the present invention and comparative examples.

FIG. 3 is a graph showing the result of comparing shock resistance testsbetween embodiments of the present invention and comparative examples.

FIG. 4 is a flowchart of a method for manufacturing a double-sided tapefor a touch screen panel according to an exemplary embodiment of thepresent invention.

FIG. 5 is a flowchart of a method for manufacturing a shock resistantfiller of a shock resistant filler layer in the double-sided tape forthe touch screen panel according to an exemplary embodiment of thepresent invention.

FIG. 6 is a configuration view of schematically showing a reactor forforming a second coating film on an expanded microsphere according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments in the present disclosure will bedescribed in detail with reference to the accompanying drawings. Thedisclosure may, however, be exemplified in many different forms andshould not be construed as being limited to the specific embodiments setforth herein.

Unless explicitly stated to the contrary, the word “comprise,”“comprises” or “comprising” used throughout the specification will notbe understood as the exclusion of the other elements but to imply theinclusion of the other elements.

FIG. 1 is a side sectional view of a double-sided tape for a touchscreen panel according to an exemplary embodiment of the presentinvention.

With reference to FIG. 1, the double-sided tape 100 for the touch screenpanel according to the exemplary embodiment, comprises a base film 10; ashock resistant filler layer 20; first and second adhesive layers 30,40; and a release layer 50. Herein the double-sided tape 100 for thetouch screen panel may formed at a total thickness of 100-300 μm.However, the present invention is not limited thereto.

The base film 10 which is a layer to be a base of the double-sided tape100 may be preferably formed of polyethylene terephthalate (hereinafterreferred to as “PET”), but the present invention is not limited thereto.For example, the base film 10 may be manufactured by applying graphitewith excellent heat resistance and heat conductivity or a conductivematerial for the addition of radiating and conductive functions.

Further, for example, a urethane base and the like may be applied to aprimer applied to the base film 10, but the present invention is notlimited thereto. The PET has an advantage of securing workability ofeasily removing the double-sided tape when the defects were generateddue to wrong assembling at the adhesive layer, and reassembling asneeded.

Further, the thickness of the base film 10 may be, for example, 20-40μm. For example, when a total thickness of the double-sided tape 100 is250 μm or less, the thickness of the base film 10 may be about 23 μm,and when the total thickness of the double-sided tape 100 is greaterthan 250 μm, and, for example, the total thickness is about 300 μm, thethickness of the base film 10 may be about 38 μm.

Herein, when the thickness of the base film 100 is less than 20 μm, theproblem of lowering heat resistance of the double-sided tape 10 andshortening a material may occur, and when the thickness of the base film10 is greater than 40 μm, because the shock resistant filler layer 20,the first and second adhesive layers 30, 40 and the like should berelatively thinly formed, the shock resistance and the adhesion of thedouble-sided tape 100 may be decreased, which is problematic. The basefilm 10 having the thickness can apply all to a touch screen windowpanel and the like, formed of acryl or a glass raw material. However,the thickness of the base film of the double-sided tape of the presentinvention is not necessarily limited to the numerical values describedabove.

Further, a surface of the base film 10 may turn black. When the surfaceof the base film 10 turns black, the function of shading the light isgiven to the base film 10, and the base film 10 can serve as preventingthe light transferred to a backlight unit from escaping to a frame partof a display. Furthermore, the adhesive forces to the first and secondadhesive layers 30, 40 respectively disposed on upper and lower sides ofthe base film 10 can be further improved.

Herein, the black coloring agent may comprise at least one of carbonblack capable of exhibiting black and iron sulfide. Further, the carbonblack may use a urethane-based resin as a binder. The urethane-basedresin has a stable physical property, and an excellent adhesive force toan acrylic-based adhesive layer. In the exemplary embodiment, the blackcoloring agent may be manufactured by mixing part of various materialsaccording to the color and the physical property as needed. However, theblack coloring agent of the present invention is not limited to thespecific ingredient or the content described above.

The shock resistant filler layer 20 is formed on the upper side of thebase film 10. Further, the thickness of the shock resistant filler layer20 varies according to the total thickness of the double-sided tape 100,and may be, for example, 60-80 μm.

Further, a surface of the shock resistant filler layer 20 may turn blackas needed. When the surface of the shock resistant filler layer 20 turnsblack, the function of shading the light is given to the shock resistantfiller layer 20, and thus, the degradation of the reliability forpartial defects due to the function of shading the light can beprevented. Herein, the black coloring agent may comprise at least one ofcarbon black and iron sulfide.

In a prior-art double-sided tape having a PE-foam structure, a PE-foammay be transferred to a base film or an adhesive layer in contactvertically in reworking. However, since the exemplary embodimentcontains the shock resistant filler layer 20 and does not use thePE-foam, it does not cause such a problem.

Such a shock resistant filler layer 20 may be formed by coating a pastecontaining an acrylic binder and the shock resistant filler on the upperside of the base film 100.

The acrylic binder may be formed of, for example, acrylonitrile.However, the present invention is not limited thereto. Meanwhile, theshock resistant filler layer 20 may further comprise additives such as across linker, a tackifier and the like, as needed. The additives may beadded at a content of 0.1-30 parts by weight, with respect to 100 partsby weight of the acrylic binder. However, the present invention is notlimited thereto.

Further, shock resistance and density of the shock resistant fillerlayer 20 may vary according to the content of the shock resistant fillercontained in the acrylic binder. For example, the shock resistant fillermay comprise 5-60 parts by weight with respect to 100 parts by weight ofthe acrylic binder.

Since the shock resistant filler is an impurity, when it exceeds 60parts by weight with respect to 100 parts by weight of the acrylicbinder, it has a low combination with the acrylic binder. Hence, as thepaste is split and coating is not available, the original function ofthe shock resistant filler cannot be carried out. Further, when thecontent of the shock resistant filler is less than 5 parts by weightwith respect to 100 parts by weight of the acrylic binder, the problemof lowering the shock resistance and repellent resistance may occur.

Further, the shock resistant filler comprises a plurality of hollow fineparticles 21 with low density. Herein, the hollow fine particles 21 haveproper cushiness and can provide shock resistance.

The hollow fine particles 21 are particles having hollow parts formedtherein, and may be manufactured in various forms in a various methods.Exemplary embodiments will be described below.

Further, the hollow fine particles 21 may comprise liquid hydrocarbonand a first coating film disposed on an outer surface thereof byreferring to the liquid hydrocarbon as a nucleating agent. After theliquid hydrocarbon serves as forming the first coating film, it isremoved in a polymerizing process described below.

The liquid hydrocarbon may comprise, for example, 1-10 parts by weightof 2-methyl butane, and 1-10 parts by weight of 2-methyl propane, withrespect to a total of 100 parts by weight of the hollow fine particles21.

Herein, in the liquid hydrocarbon, when the content of the 2-methylbutane is less than 1 part by weight, inner expansion is insufficient inmanufacture of the hollow fine particles 21, and thus the problem oflowering the shock resistance of the hollow fine particles 21 may occur.Further, when the content of the 2-methyl butane is greater than 10parts by weight, there is overexpansion in manufacture of the hollowfine particles 21, and thus the hollow fine particles 21 do not keep aconstant type to lower uniformity, thereby decreasing an overallphysical property.

Further, when the content of the 2-methyl propane is less than 1 part byweight, inner expansion is insufficient in manufacture of the hollowfine particles 21, and thus the problem of lowering the shock resistanceof the hollow fine particles 21 may occur. Further, when the content ofthe 2-methyl butane is greater than 10 parts by weight, there isoverexpansion in manufacture of the hollow fine particles 21, and thusthe hollow fine particles 21 do not keep a constant type to loweruniformity, thereby decreasing an overall physical property.

The first coating film may comprise a thermoplastic material containinga monomer. The thermoplastic material may comprise 15-40 parts by weightwith respect to a total of 100 parts by weight of the hollow fineparticles 21. The thermoplastic material may comprise, for example, acopolymer of acrylonitrile and other acrylic groups, but thethermoplastic material of the present invention is not limited thereto.The other acrylic groups may comprise phosphate methacrylate, alkalistrippable polyester acrylate and the like.

Herein, when the content of the thermoplastic material is less than 15parts by weight, because it has an impact on crosslink density, acoating treatment may not be smoothly performed. Further, when thecontent of the thermoplastic material is greater than 40 parts byweight, because it has an impact on the content of the shock resistantfiller, the shock resistance and the reliability may be lowered.

The first coating film supplies elastic and restoring forces to thedouble-sided tape 100, and supplies the shock resistance thereto toserve as supply of a tolerance to mechanical distortion. For example,even if a load of about 0.7 Mpa is repetitively applied to thedouble-sided tape 100, the double-sided tape 100 is not damaged with theelastic and restoring forces of the first coating film.

Meanwhile, the hollow fine particles 21 may further comprise a secondcoating film arranged along the circumference of the first coating film,as needed. The second coating film may comprise 50-80 parts by weight ofcalcium carbonate with respect to 100 parts by weight of the hollow fineparticles 21. The second coating film improves a shattering property ofthe liquid hydrocarbon, and improves dispersibility in a resin of thefirst coating film, thereby having an effect of further improving theshock resistance of the hollow fine particles 21.

Further, the second coating can increase a gravity of the hollow fineparticles 21 while preventing the hollow fine particles 21 from beingcondensed in the shock resistant filler, and can serve as improving amixing property.

Herein, when the content of the calcium carbonate is less than 50 partsby weight, workability may be decreased because of shattering the shockresistant filler, and when the content of the calcium carbonate isgreater than 80 parts by weight, the shock resistance may be lowered.

Meanwhile, the diameter of the hollow fine particles 21 of the exemplaryembodiment may be 10-50 μm, wherein an inner through-hole which theliquid hydrocarbon occupies in the step of manufacturing the hollow fineparticles 21 accounts for 95%, and the thicknesses of the first andsecond coating films may be 1 μm or less in totality. The diameter ofthe hollow fine particles 21 keeps the uniformity of a product in theforegoing scope to minutely adjust the level of illumination, therebyensuring a step compensation of the product and stability of theadhesive power. However, the present invention is not limited thereto.

Meanwhile, since the shock resistant filler layer 20 uses the hollowfine particles 21 having the uniform diameter described above, it has anexcellent level of illumination in general. In addition, since it issoft like a sponge, it properly fills even the nonuniform level ofillumination of an injection product, thereby securing the adhesivepower and the reliability. For example, when it is used in an interfacebetween a panel module and a liquid crystal module of the touch screen,it easily permeates into a gap between the panel module and the liquidcrystal module, thereby greatly increasing adhesion.

The first and second adhesive fillers 30, 40 are formed on an upper sideof the shock resistant filler layer 20, and a lower side of the basefilm 10, respectively. The first and second adhesive fillers 30, 40 maybe formed of, preferably, an acrylic-based pressure sensitive adhesiveagent, but the present invention is not limited thereto. Further, thefirst and second adhesive fillers 30, 40 can adjust the contents ofe-EHA, CHMA and nBA, so as to embody excellent water resistance,adhesive power and reliability in polymerization of the acrylic-basedadhesive agent.

Herein, the first and second adhesive layers 30, 40 may have differentadhesive powers according to adhered objects. Hence, the first adhesivelayer 30 may be formed to have a different thickness, and, for example,it may be formed to be thicker by about 10 μm than the second adhesivelayer 40 formed between the base film 10 and a release layer 50.

Further, as the first adhesive layer 30 or the second adhesive layer 40gets thicker by a critical thickness, the adhesive power thereof isincreased. Thus, the adhesive layer is made as thick as possible, fromwhich the adhesive power can be improved, and also, the adhesive layeritself can provide a constant cushioning property. When the firstadhesive layer 30 or the second adhesive layer 40 is too thin, theadhesion is lowered, and when the first adhesive layer 30 or the secondadhesive layer 40 is too thick, it may have an impact on blankingmolding in a blanking process.

Further, the first and second adhesive layers 30, 40 controls theirsoftness by adjusting crosslink density, thereby further improving theshock resistance and providing a step compensation effect according to astacking structure. Herein, the crosslink density can be adjusted bycontrolling the kinds and the contents of hardening agents.

The release layer 50 may be formed on a lower side of the secondadhesive layer 40. The release layer 50 serves as preventing thefinished tape 100 from having foreign substance or being damaged whenthe double-sided tape 100 is stored or transported. The release layer 50can uses, for example, a product in which a PE film is connected topaper and silicon is release-treated on an outer surface of the PE film.However, the present invention is not limited thereto. For example, therelease product 50 may use the product in which silicon isrelease-treated in glassine and PET goods. Acryl and silicon areincompatible and are not thus coupled to each other, and as a result, anacrylic adhesive agent may use a product in which the release film issilicon-treated.

In an exemplary embodiment of the present invention, the thickness ofthe paper may be 70-80 μm, and the PE film of which the thickness is30-40 μm may be used on its double sides. Further, for therelease-treatment of the silicon, the silicon may be coated with a thinfilm having a thickness of 1 μm or less. Herein, according to the kindof the used silicon, release powers and transition rates of the releaselayer 50 may be different, and, typically, the release layer 50 uses thetransition rate of 90% or more. Herein, the transition rate indicates anumerical value of moving silicon to acryl, wherein the low transitionrate indicates the small change in a physical property.

Herein, from the comparison between the comparative examples and theembodiments of the present invention, the excellent characteristics ofthe double-sided tape according to the present invention will bedescribed below.

Comparative Example 1 shows a double-sided tape having an acrylic-foamstructure having a total thickness of 200 μm, Comparative Examples 1 to4 show double-sided tapes having polyethylene-foam structures of whichtotal thicknesses are 250 μm, 200 μm and 200 μm, respectively, andEmbodiments 1 to 3 show double-sided tapes having shock resistant fillerlayers of which total thicknesses are 200 μm, 250 μm and 300 μm,respectively.

Herein, in Embodiment 1, the thicknesses of the first and secondadhesive layers were 60 μm, and the thickness of the shock resistantfiller layer was 60 μm. In Embodiment 2, the thicknesses of the firstand second adhesive layers were 70 μm, and the thickness of the shockresistant filler layer was 70 μm. In Embodiment 3, the thicknesses ofthe first and second adhesive layers were 90μm, and the thickness of theshock resistant filler was 80 μm. In Embodiments 1 to 3, the contents ofthe shock resistant fillers in all the shock resistant filler layersused 35 parts by weight with respect to 100 parts by weight of theacrylic binder.

Hereinafter, Embodiments 1 to 3 will be referred to as “the embodiments”and described as needed when describing features irrelevant to the totalthickness.

An adhesive power test is called an ASTM D 3330 test, wherein thedouble-sided tapes of the comparative examples and the embodimentsadhered to an SUS board, a PC board and glass, respectively, byreciprocating 2 kg of a rubber compressing roller one time at a velocityof 300 mm/min, and then, they were left for 30 minutes at roomtemperature. The forces (gf/25 mm) of detaching the double-sided tapesfrom adhered objects were measured.

With reference to FIG. 2, as a result of the measurement, it can beconfirmed that both upper and lower sides in Embodiments 1 to 3 aresimilar to or have relatively higher force values than those ofComparative Examples 1 to 4. Thus, it can be known that the double-sidedtapes having the shock resistant filler layers of the embodiment of thepresent invention are similar to or have more excellent adhesion thanthe double-sided tapes having the acrylic foam or the PE-foam(Comparative Examples 1 to 4).

As a result, the comparative examples should additionally use anadhesive so as to reduce a difference of such adhesion. The use of theadhesive makes it impossible to carry out rework of separating thedouble-sided tape from the adhered object and reassembling it as needed,and also leads to several problems such as rise in costs, a complicatedmanufacturing process and the like.

The test of the shock resistance is for measuring a restoring forceaccording to pressure applied to the product. With reference to FIG. 3,as a result of the measurement, the embodiments have a smaller change inthe thickness as per the pressure applied to the product than thecomparative examples, and have a smaller compression rate as per thepressure applied to the product than the comparative examples. Herein,the unit of a compression thickness is μm, the unit of a compressionstr. is mPa, and the unit of a compression rate is %. In the test of theshock resistance, conventional products using the PE-foam are used onlyin Comparative Examples 2 and 3 .

In general, when the double-sided tape applies to the touch screenpanel, there may be cracks or peeling on the upper and lower plates dueto artificial impacts. The test result shows that in the comparativeexamples, when the characteristic of low elasticity and low density andthe pressure are applied to the tapes, they have slow restoring forces.In contrast, in the embodiments, the shock resistant filler formed ofthe hollow fine particle of the shock resistant filler layer play a roleas a spring to improve the shock resistance with the characteristic ofhigh elasticity and high density, and when pressure is applied to thetapes, they have fast restoring forces.

It can be expected that the shock resistance of the double-sided tapeaccording to the exemplary embodiments of the present invention is moreimproved by average 300% or more than the comparative examples. Thus,the embodiments have a compression rate of about 50% for the comparativeexamples, and have excellent repellent resistance to restrain impactsfrom being applied to an ITO sensor although the tape is not made thick.Thus, it can be known that even if the product having a thickness of 300μm to which the comparative examples applies is manufactured to have thethickness of 200-250 μm in the embodiments, it can exhibit the shockresistance equal to or superior to that of the embodiments.

Meanwhile, the difference of the shock resistance of the double-sidedtape may cause a remarkable difference even in a waterproof property ofthe touch screen panel because of the cracks or peeling. That is, evenif the double-sided tapes are manufactured to have the same thickness,the double-sided tapes in the comparative examples and the embodimentshave remarkably different shock resistance.

In other words, according to the embodiments of the present invention,waterproofing performance of IP×7 or more can be implemented due to suchshock resistant difference, while the comparative examples implementsmuch lower waterproofing performance than the embodiments. Herein, IPmeans IP_Ingress Protection rating, the first number x indicatesclassifying a grade for a dust proof function into 0-6, and the secondnumber indicates classifying a grade for a waterproof function into0-9k. A higher number indicates excellent performance.

Further, in the double-sided tapes according to the embodiments of thepresent invention, since pressure in adhering by the shock resistantfiller layer focuses on a binding portion to easily extrude air presentin an adhesion interface, excellent adhesion that prevents a gap throughwhich water are penetrated can be implemented, in connecting rigidbodies, thereby improving a waterproof property.

Further, according to the exemplary embodiment of the present invention,a thickness direction of the double-sided tape has more excellent stepcompensation by the shock resistant filler layer than the comparativeexample, which can give a great advantage to the waterproof property.

Meanwhile, the conventional double-sided tapes for touch screen panelshave a so-called open cell structure that a foaming agent is insertedinto a PE resin in manufacture to make openings, and the openings giverise to cushiness. Herein, they have problems such as a big thicknessdeviation of 20-30 μm, and an ununiform surface.

However, the double-sided tape 100 for the touch screen panel accordingto the exemplary embodiment of the present invention does not use such aPE-foam, and has a so-called closed cell structure using the shockresistance filler layer. Thus, in accordance with the embodiment, sincethe thickness of the tape is adjusted by coating unlike the conventionaldouble-sided tape having the open cell structure, the tape can have auniform thickness on the whole. Also, since the shock resistant fillerlayer is formed by a coating process, its thickness can be easilyadjusted to have excellent productivity and wetting. In the conventionalPE-foam, it is difficult to have a distribution value of a uniformthickness.

In addition, the tensile strength of the adhesive layer and the shockresistant filler layer may be about 2 kgf/mn², and the physical propertymay be 30 kgf/mm² or less according to the tensile strength of PET asthe base film.

Hereinafter, a method for manufacturing a double-sided tape 100 for atouch screen panel according to an exemplary embodiment of the presentinvention will be described below.

FIG. 4 is a flowchart of a method for manufacturing a double-sided tapefor a touch screen panel according to an exemplary embodiment of thepresent invention.

With reference to FIG. 4, the base film 10 first turns black (S1).Herein, the black coloring agent may use at least one of carbon blackand iron sulfide. Furthermore, it is preferable to properly mix and usethe carbon black or the iron sulfide to prevent part of the base film 10from being lumped to turn. The carbon black or the iron sulfide ispreferably sufficiently stirred at 300 rpm or less for 10-30 minutes soas not to affect uniform stirring and a physical property. However, thepresent invention is not limited thereto.

Next, the shock resistant filler layer 20 is formed by coating a pastecontaining a shock resistance filler having the acylic binder and aplurality of hollow fine particles 21 on the upper side of the base film10 (S2). Herein, the shock resistant filler may comprise 5-60 parts byweight with respect to 100 parts by weight of the acrylic binder.Further, it may further comprise an additive containing 0.1-30 parts byweight of a cross linker, as needed. Herein, the shock resistant fillerlayer 20 may turn black as needed.

FIG. 5 is a flowchart of a method for manufacturing a shock resistantfiller of the shock resistant filler layer in the double-sided tape forthe touch screen panel according to an exemplary embodiment of thepresent invention. With reference to FIG. 5, an exemplary embodiment ofa method for manufacturing the hollow fine particle is described asfollows.

First, 2-20 parts by weight of liquid hydrocarbon and a dispersing agentare inputted into 0.1-1 parts by weight of water, with respect to atotal of 100 parts by weight of the follow fine particle 21.

Herein, the liquid hydrocarbon may comprise, for example, 1-10 parts byweight of 2-methylbutane and 1-10 parts by weight of 2-methylpropane.Further, the dispersing agent may be a moderate amount of a surfactant.Thereafter, the hydrogen dispersion is prepared by dispersing the liquidhydrocarbon not mixed with water, at a certain size, by using thesurfactant (S21).

Herein, additives such as a cross linker and the like may be furtherinputted thereto, as needed. The size limitation of the additives can beadjusted by the gravity. When the size of the filler gets bigger, andporous layers of the hollow fine particles grow bigger, the shockresistant filler layer 20 has a low gravity, and when the filler getssmaller than the standard, the porous layers of the hollow fineparticles get smaller, and the gravity thus grows bigger.

Thereafter, a thermoplastic material containing a monomer is inputtedinto the dispersed liquid hydrocarbon, the dispersed liquid hydrocarbonis referred to as a nucleating agent, and then, a first coating film tosurround the liquid hydrocarbon is formed, thereby preparing aparticulate crystal (S22).

Herein, the monomer may comprise a copolymer of 15-40 parts by weight ofacrylonitrile with respect to a total of 100 parts by weight of thehollow fine particle and other acylic groups.

Thereafter, the particulate crystal having the first coating film formedthereon is polymerized (S23). The polymerization is that for example,0.1-5.0 parts by weight of a polymerization initiator is added to theliquid hydrocarbon and is heated at a temperature of 140-150° C. for10-60 minutes, from which the particulate crystal is heated to removethe hydrocarbon, thereby preparing an unexpanded microsphere is prepared(S24). Herein, the polymerization may proceed through a manner ofseparating the first coating film from the liquid hydrocarbon with adifference of the gravity, as needed.

Thereafter, the unexpanded microsphere is heated, for example, for 10-60minutes to expand the diameter of the first coating film, and as aresult, an expanded microsphere having an expanded volume in comparisonwith the originally provided unexpanded microsphere is prepared (S25).Herein, the unexpanded microsphere may be heated, for example, for110-190° C., and more preferably, for 130-170° C. However, the presentinvention is not limited thereto. When the heating temperature is lessthan 110° C., microsphere is insufficiently expanded, which may lead tothe problem of lowering repellent resistance and chemical stability ofthe hollow fine particles. Further, when the heating temperature isgreater than 190° C., since the repellent resistance is lowered,chemical resistance and storage stability are vulnerable, and it may bedifficult to implement the characteristic of the product.

That is, when the liquid hydrocarbon is referred to as the nucleatingagent, and the outer wall is surrounded by an acrylic monomer, theparticulate crystal is polymerized to remove the liquid hydrocarbon.Then, the first coating film is expanded to form the microsphere whichhas the porous layer formed thereon, has a hollow part and has anexpanded volume, thereby manufacturing the shock resistant filler havingthe expanded microsphere.

Thereafter, a second coating film containing 50-80 parts by weight ofcalcium carbonate with respect to a total of 100 parts by weight of thehollow fine particles may be further disposed on the circumference ofthe first coating film of the expanded microsphere, as needed.

With reference to FIG. 6, in the second coating film, for example, theexpanded microsphere (M) and calcium carbonate (C) are inserted into amain body 210 of a reactor 200 through injection parts 221-224 formed ina pipe shape, and hot air having a temperature of about 130-150° C. isinserted thereto through an air supply part 251, thereby allowing theexpanded microsphere (M) and the calcium carbonate (C) to float in themain body 210 of the reactor 200. In this state, the second coating filmmay be progressed to be formed while the calcium carbonate (C) bumpsagainst the circumference of the first coating film of the expandedmicrosphere (M) and is embedded therein.

Herein, the velocity of supplying the air inserted into the main body210 of the reactor 200, and the like, can be controlled to the extentthat the expanded microsphere (M) and the calcium carbonate (C) canproperly float and flow in the main body 210 of the reactor 200.Further, in the main body 210, a rotating shaft 231 having a propeller231 a may be installed to circulate the inserted air, the expandedmicrosphere (M) and the calcium carbonate (C) and to more smoothly formthe second coating film. Further, the temperature of the air makes thefirst coating film tender to easily embed the calcium carbonate (C) onthe circumference thereof. However, the temperature of the air accordingto the present invention is not limited thereto. Furthermore, in a lowerend of the main body 210, a discharge part 241 having a valve 241 a maybe prepared to discharge the microsphere (M) having the second coatingfilm formed thereon.

The second coating film serves as restraining condensation and ashattering property of the expanded microsphere (M). Further, thedensity is measured by comparing the amount of the thermoplasticmaterial inputted in the foregoing step and the amount and weight of aplurality of hollow fine particles finally completed, as needed. Thus,the density of the hollow fine particles can be uniformly maintained.Furthermore, the shock resistant filler in the embodiments is light in ahardening process to floats at the top, all of which escapes in air.

Meanwhile, by randomly extracting samples and measuring their gravities,it can be confirmed whether the shock resistant filler layer 20 has auniformly sized distribution or not. When the shock resistant fillerlayer 20 comprises large numbers of big fillers, it is lighter than asuitable standard sample, and when it comprises large numbers of smallfillers, it is heavier than the suitable standard sample.

In accordance with the embodiments, as described above, the danger ofextinguishing the liquid hydrocarbon in the shock resistant filler layerat a high temperature, and shattering the particles of the porous layermay occur. However, the second coating film gives a fixed weight to theexpanded microsphere (M) to improve the dispersibility of the firstcoating film of the expanded microsphere (M). As a result, the secondcoating film serve as preventing the hollow fine particles 21 from beshattered, and can provide an effect of improving the shock resistanceof the hollow fine particles 21.

Further, the second coating can serve as increasing gravities of thehollow fine particles 21 while preventing the hollow fine particles 21from being condensed in the shock resistant filler, and can serve asimproving a mixing property.

Herein, the second coating film may comprise 50-80 parts by weight ofcalcium carbonate with respect to 100 parts by weight of the hollow fineparticles 21. Herein, when the content of the calcium carbonate is lessthan 50 parts by weight, workability may be decreased because ofshattering the shock resistant filler, and when the content of thecalcium carbonate is greater than 80 parts by weight, the shockresistance may be lowered.

Next, the first and second adhesive layers 30, 40 are formed on theupper side of the shock resistant filler layer 20 and the lower side ofthe base film 10, respectively (S3).

Next, the release layer 50 is formed on the lower side of the secondadhesive layer 40 to complete the double-sided tape for the touch screenpanel (S4).

The present invention should not be construed as limited to theembodiments set forth herein and the accompanying drawings, and is onlydefined by scopes of claims.

Thus, it will be apparent to those skilled in the art that replacements,modifications, and variations can be made without departing from thespirit and scope of the invention.

10; a base film

20; a shock resistant filler layer

21; hollow fine particles

30, 40; first and second adhesive layers

50; a release layer

100; a tape

200; a reactor

What is claimed is:
 1. A double-sided tape for a touch screen panelcomprising: a base film; a shock resistant filler layer formed on thebase film and comprising acrylic binder and an shock resistant fillercontaining 5-60 parts by weight with respect to 100 parts by weight ofthe acrylic binder; first and second adhesive layers formed an upperside of the shock resistant filler layer and a lower side of the basefilm, respectively; and a release layer formed on a lower side of thesecond adhesive layer, wherein the shock resistant filler of the shockresistant filler layer comprises a plurality of hollow fine particles.2. The double-sided tape for a touch screen panel of claim 1, whereinthe hollow fine particles comprise a first coating film formed of athermoplastic material containing 15-40 parts by weight of a monomer,with respect to a total of 100 parts by weight, and having a hollowpart.
 3. The double-sided tape for a touch screen panel of claim 1,wherein the hollow fine particles further comprise a second coating filmcontaining 50-80 parts by weight of calcium carbonate, with respect to atotal of 100 parts by weight, and arranged along the circumference ofthe first coating film.
 4. The double-sided tape for a touch screenpanel of claim 1, wherein the monomer of the first coating film is acopolymer comprising at least one of 15-40 parts by weight ofacrylonitrile, with respect to 100 parts by weight of the hollow fineparticle, phosphate methacrylate and alkali strippable polyesteracrylate.
 5. The double-sided tape for a touch screen panel of claim 1,wherein at least one of the base film and the shock resistant fillerlayer may turn black, and the black coloring agent comprises at leastone of carbon black and iron sulfide.
 6. The double-sided tape for atouch screen panel of claim 1, wherein the hollow fine particlescomprise: liquid hydrocarbon comprising 1-10 parts by weight of 2-methylbutane and 1-10 parts by weight of 2-methyl propane, with respect to atotal of 100 parts by weight; a first coating film formed of athermoplastic material comprising a copolymer containing at least one of15-40 parts by weight of acrylonitrile, phosphate methacrylate, alkalistrippable polyester acrylate, and formed to surround the liquidhydrocarbon; and a second coating film formed of 50-80 parts by weightof calcium carbonate, and formed to surround the first coating film. 7.A method for manufacturing a double-sided tape for a touch screen panel,comprising the steps of: coloring a base film black; forming a shockresistant filler layer by coating a paste containing a shock resistantfiller having an acrylic binder and a plurality of hollow fine particleson an upper side of the base film; forming first and second adhesivelayers on an upper side of the shock resistant filler layer and a lowerside of the base film, respectively; and forming a release layer on alower side of the second adhesive layer, wherein the hollow fineparticles are manufactured by the steps of: preparing a hydrogendispersion by inputting 2-20 parts by weight of liquid hydrocarbon withrespect to a total of 100 parts by weight and a dispersing agent intowater; preparing a particulate crystal by inputting 15-40 parts byweight of a monomer into the hydrogen dispersion, with respect to atotal of 100 parts by weight of the hollow fine particles, and forming afirst coating film on the circumference of the hydrocarbon; forming anunexpanded microsphere by heating the particulate crystal and removingthe hydrocarbon; and preparing an expanded microsphere by heating theunexpanded microsphere to expand the first coating film.
 8. The methodfor manufacturing a double-sided tape for a touch screen panel of claim7, wherein the hollow fine particles are manufactured by furthercomprising the step of arranging a second coating film containing 50-80parts by weight of calcium carbonate with respect to a total of 100parts by weight of the hollow fine particles, on the circumference ofthe first coating film of the expanded microsphere.
 9. The method formanufacturing a double-sided tape for a touch screen panel of claim 7,wherein, in the step of preparing the hydrogen dispersion, the liquidhydrocarbon comprises 1-10 parts by weight of 2-methylbutane and 1-10parts by weight of 2-methylpropane, with respect to a total of 100 partsby weight of the hollow fine particles.
 10. The method for manufacturinga double-sided tape for a touch screen panel of claim 7, wherein thedispersing agent is a surfactant in the step of preparing the hydrogendispersion.
 11. The method for manufacturing a double-sided tape for atouch screen panel of claim 7, wherein the monomer is a copolymer of15-40 parts by weight of acrylonitrile with respect to a total of 100parts by weight of the hollow fine particles and other acrylic groups,in the step of preparing the particulate crystal.
 12. The method formanufacturing a double-sided tape for a touch screen panel of claim 7,wherein the unexpanded microsphere is heated at a temperature of 70-190°C., in the step of preparing the expanded microsphere.
 13. The methodfor manufacturing a double-sided tape for a touch screen panel of claim7, where the step of forming the second coating film comprises the stepsof: inputting the expanded microsphere and the calcium carbonate into areactor, and inserting air thereto at a temperature of 130-150° C.,thereby floating the expanded microsphere and the calcium carbonateinside the reactor; and forming a second coating film while embeddingthe calcium carbonate on an outer wall of the first coating film of theexpanded microsphere.
 14. The method for manufacturing a double-sidedtape for a touch screen panel of claim 7, wherein at least one of carbonblack and iron sulfide is used as the black coloring agent, in the stepof coloring the base film black.
 15. The method for manufacturing adouble-sided tape for a touch screen panel of claim 7, wherein the shockresistant filler contains 5-60 parts by weight with respect to 100 partsby weight of the acrylic binder, in the step of forming the shockresistant filler layer.